Fingerprint sensing and matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. Nos. 5,963,679 and 6,259,804 and assigned to the assignee of the present invention, the entire contents of which are incorporated herein by reference. The fingerprint sensor is an integrated circuit sensor that drives the user's finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate. Additional finger sensing integrated circuits and methods are disclosed in U.S. Published U.S. patent application Ser. No. 2005/0089202 entitled “Multi-biometric finger sensor including electric field sensing pixels and associated methods”, also assigned to the assignee of the present invention, and the entire contents of which are incorporated herein by reference.
One type of integrated finger sensor is a so-called slide or swipe sensor that includes a relatively small rectangular sensing surface over which the user slides or swipes his finger. It may be desired to generate a global image of the user's finger from data collected from the slide sensor. Indeed, the prior art may be considered as include two classes of system design philosophies for constructing the global image from a slide sensor. One class uses various types of finger speed sensors to either control the sampling rate or discard repeated data, such as disclosed, for example, in U.S. Pat. No. 6,002,815. Another class uses cross correlation between partially overlapped image frames to eliminate redundant data and stitch together into a single global image, such as disclosed in U.S. Pat. No. 6,289,114.
These prior approaches suffers from certain disadvantages. For example, two separate processes may be required for image deskewing and partial image stitching. They may lack a mechanism to reduce noise caused by non-uniform finger movement effects, may have no mechanism to reduce sensor fixed pattern noise, and may not easily adapt to widely varying finger speeds. Of course, when the finger slides at slower speeds, extra data is typically discarded.